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<head>
    <meta charset="UTF-8">
    <title>left</title>
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<body>
<ul>
   	<li><a target = "main" href = "1.html">作业一</a></li>
	<li><a target = "main" href = "2.html">作业二</a></li>
	<li><a target = "main" href = "3.html">作业三</a></li>
</ul>
</body>
</html>